1. Field of the Invention
The present invention relates to a grating adjustment apparatus of a 3-beam type optical pick-up and, more particularly, to an improved grating adjustment apparatus used in assembling of a 3-beam type optical pick-up for automatically and readily adjusting a grating angle to obtain a tracking error signal which is larger than the designated value in condition that two sub-beams of 3 laser beams are scanned on the same track of a compact disk.
2. Description of the Prior Art
As for a tracking method of a compact disk player using three laser beams, grating adjustment plays an important role in stability of a tracking servo. Grating adjustment must be made to obtain the maximum magnitude of a tracking error, but it is inconvenient to adjust the magnitude of a tracking error minutely with a manual adjustment means. In details, if a tracking error is observed and adjusted with an equipment such as a voltmeter or an oscilloscope, it is very difficult to measure a tracking error with the naked eye because a tracking error TE is .SIGMA..vertline.a(w).vertline.e.sup.jwt. Though a general low pass filter is also utilized, an accurate grating adjustment cannot be accomplished in the end.
Furthermore, because a grating degree adjustment extent of a general optical pick-up is restricted within a target value .+-.0.3.degree., it is so difficult to be adjusted accurately by the hand and therefore, it has demerit that work efficiency was dull.